Hierarchical routing query method of automatic switched optical network

ABSTRACT

A hierarchical route inquiry method in Automatic Switched Optical Network is applied to the networks having multi-layer route domains. According to the method, after the route controller RC in one child domain receives the Route Request, if it can not calculate the complete route, it sends the Route Request to the RC in the parent domain; if the RC in the parent domain can not obtain the complete route, it further interacts with other child domains to obtain the complete route and returns the Route Response back to the requester. The present invention solves the problem of creating a cross-domain connection in route inquiry in the Automatic Switched Optical Network.

CROSS REFERENCE RELATED APPLICATIONS

This application is a national phase of PCT/CN2006/003250 filed Dec. 1,2006, which is entirely incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to the field of optical networks, and morespecifically to a hierarchical route inquiry method in an automaticswitched optical network.

BACKGROUND ART

Optical networks, such as OTN (Optical transmission network), WDM(Wavelength-division multiplexing), SDH (Synchronous digital hierarchy)or SONET (Synchronous optical network), have been widely applied in thetelecommunication field.

Recently, the automatic switched optical network (ASON) is one ofresearch hotspots in the field of optical networks. The concept of ASONis offered by ITU-T G.8080, in which the function of ASON is achieved bysetting a specific Control Plane (CP). ITU-T G.7713 specifies theframework to implement the distributed calls and connections in ASON tooffer the implementation criterion for automatically establishing,modifying and deleting the calls and connections. Standards such asITU-T G.7715 offer the implementation model and method for the routeinquiry of the connection (the route inquiry described in the followingwill refer to the route inquiry of the connection, unless especiallydeclared).

However, both the published ITU-T G.7715 and ITU-T G.7715.1 apply themodel shown in FIG. 1. In this route model, when an ASON network element(NE for short) needs to query the connection route, the ConnectionController (CC) responsible for the connection control (includingestablishment, deletion, modification, and so on) sends the routeinquiry request (Route Request for short) to the Route Controller (RC)responsible for the route inquiry and calculation, and then the RC callsa routing algorithm (a typical routing algorithm is Constrained ShortestPath First, shortly CSPF) according to the Route Request and calculatesthe route based on the Route Data Base (RDB) of the current node andreturns the route inquiry result (Route Response for short) to the CC.

However, the RDB of a node generally is hard to have the complete routeinformation of the whole ASON, especially when the ASON has severalroute domains. The RDB of one node always has only the information oflocal route domain. FIG. 2 shows the situation when one ASON has severalroute domains, which shows that when a connection should be establishedbetween A in route domain 1 and K in the route domain 4, as shown by thedot line, the model shown in FIG. 1 can not meet the requirement of theroute inquiry and calculation of the connection.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to offera method of hierarchical route inquiry in ASON to solve the problem ofroute inquiry in cross-domain connection.

In order to solve the above technical problem, the present inventionoffers a method of hierarchical route inquiry in ASON, which is appliedin the network that comprises multi-layer route domains. In the method,when the RC of a child domain receives the Route Request, it sends theRoute Request to the RC of the parent domain if it can not calculate acomplete route, and the RC of the parent domain further interacts withother child domains to obtain the complete route if it can not calculatea complete route, and then sends the Route Response to the requester.

Furthermore, the above method may also have the following feature: themethod further comprises the following steps:

(a1) After the RC of a NE in ASON detects the Route Request from therequester, it forwards the Route Request to the RC of the parent domainif the Request is a cross-domain Route Request;

(a2) The RC of the parent domain calculates the route among all itschild domains and sends an in-domain Route Request to the RC of eachchild domain on the route, the RC of each child domain calculates theroute in its own domain and returns the Route Response to the RC of theparent domain which, after receiving the Route Response, returns theroute to the requester through the RC which launches the Route requestif a complete route can be obtained through combination, otherwise afailure message is returned.

Furthermore, the method may have the following feature: the step (a2)further comprises the following steps:

(a21) The RC of the parent domain calculates the route among its childdomains, determines the boundary node of each child domain on the route,and then generates and broadcasts the in-domain Route Request includingthe information of boundary node of the corresponding child domain;

(a22) After the child domains receive the in-domain Route Request, itcalculates the route of its domain and returns the Route Response of itsown domain to the RC of the parent domain;

(a23) After the RC of the parent domain receives the Route Responsesfrom the child domains, it determines whether all results aresuccessful, if yes, then proceed to the next step; otherwise, a failuremessage is returned to the requester through the RC which launches therequest, ending;

(a24) The RC of the parent domain combines the cross-domain route andthe in-domain route of each child domain to generate the complete routebetween the start and the end, and returns the complete routing to therequester through the RC which launches the Request, ending.

Furthermore, the above method may also have the following features: ifthe parent domain fails to calculate the cross-domain route in step(a2), then a failure message is returned to the requester through the RCwhich launches the Request, ending.

Furthermore, the above method may also have the following feature: themethod further comprises the following steps:

(b1) After the RC of the NE in ASON detects the Route Request sent bythe requester, it calculates the route based on the RDB of the currentnode, and returns the Route Response to the requester if a completeroute is obtained, ending; otherwise, it forwards the Request to the RCof the parent domain;

(b2) The RC of the parent domain calculates the route based on the RDBof current node according to the Request, and if the complete route isobtained, it is returned to the requester through the RC which launchesthe Request, ending; otherwise, proceeding to the next step;

(b3) The RC of the parent domain forwards the Route Request to the RC ofits other child domains, and after it receives the Route Responses fromthe RCs of these child domains, it returns the route to the requesterthrough the RC which launches the Request if it obtains the completeroute, otherwise, a failure message is returned to the requester throughthe RC which launches the Request, ending.

Furthermore, the above method may also have the following feature: thestep (b3) further comprises the following steps:

(b31) The RC of the parent domain sends the Route Request to the RC ofone of its other child domains other than the RC which launches theRequest;

(b32) After the RC of the other child domain receives the Route Request,it calculates the route based on the RDB of the current node and returnsthe Route Response to the RC of the parent domain;

(b33) The RC of the parent domain determines whether the Route Responsereturned from the RC of the child domain is the complete route, if yes,the route is returned to the requester through the RC which launches theRequest, ending; otherwise, proceeding to the next step;

(b34) The RC of the parent domain determines whether there is a RC ofother child domain that has not been queried, if there is, the RouteRequest is further forwarded to the RC of another child domain, andturning to step (b32); otherwise, a failure message is returned to therequester through the RC which launches the request, ending.

Furthermore, the above method may also have the following feature: thestep (b3) further comprises the following steps:

(b31) The RC of the parent domain broadcasts the Route Request to theRCs of all other child domains but the one which launches the Request;

(b32) After the RCs of all other child domains receive the RouteRequest, they calculate the route based on the RDB of their currentnodes and return the Route Responses to the RC of the parent domain;

(b33) The RC of the parent domain determines whether there is a completeroute in the Route Responses returned from the RCs of the child domains,if yes, the route is returned to the Requester through the RC whichlaunches the Request, ending.

Furthermore, the above method may also have the following feature: whenthe RC of the parent domain sends the Route Request to the RC of thechild domain, the Route Request is sent to the RC of the representativeNE which represents the child domain to interact with the upper-layerroute domain.

Based on the hierarchical route model suggested by the ITU-T G.8080, themethod of the present invention realizes the route inquiry, which cannot be accomplished by the NE in the local route domain, through theinteraction of the RCs of different hierarchical route domains, easy andreliable.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of the route inquiry by a single NE;

FIG. 2 is an illustration of an ASON having several route domains;

FIG. 3 shows a model of RC interaction according to the method of thehierarchical route domain applied in the present invention;

FIG. 4 is an illustration of the process of the RC interaction inaccordance with the first embodiment of the present invention;

FIG. 5 is an illustration of the process of the RC interaction inaccordance with the second embodiment of the present invention;

FIG. 6 is an illustration of the process of the RC interaction inaccordance with the third embodiment of the present invention;

FIG. 7 is an illustration of the final Route Response in accordance withthe present invention, based on the network shown in FIG. 2;

FIG. 8 is an illustration of the RC of the parent domain calculating thecross-domain route in accordance with the third embodiment of thepresent invention, based on the network shown in FIG. 2;

FIG. 9 is an illustration of the related RC of the child domain 1calculating the in-domain route in accordance with the third embodimentof the present invention, based on the network shown in FIG. 2;

FIG. 10 is an illustration of the related RC of the child domain 2calculating the in-domain route in accordance with the third embodimentof the present invention, based on the network shown in FIG. 2;

FIG. 11 is an illustration of the related RC of the child domain 4calculating the in-domain route in accordance with the third embodimentof the present invention, based on the network shown in FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Based on the prior art, the present invention offers an implementationstrategy to solve the problem that route inquiry can not be performed bythe RC of NEs in the single route domain.

The key of the present invention is to implement the route inquirythrough the interaction between the RCs of the related NEs of ASON inthe related parent domain and the child domains based on hierarchicalroute model. In the present invention, according to manual configurationor other methods, the RC of each route domain can obtain the informationabout the RC of the upper-layer domain (the parent domain in short. Withrespect to the parent domain, the other route domains are called thechild domains).

One method is: the RC of each child domain is responsible forcalculating the route in its domain, and the cross-domain route can becalculated by sending the Route Request to the RC working in the parentdomain, and the RC of the parent domain can further use the RouteRequest to request the route across the other child domains.

Another method is: when the route inquiry should be performed, the RC ofthe local route domain calls the routing algorithm according to theRequest to calculate the route based on the RDB of the current node. Ifthe calculation fails, the RC forwards the Request to the RC of theupper-layer domain, and the route inquiry is accomplished by the RC ofthe parent domain or by the interaction between the RC of the parentdomain and the RCs of the other child domains.

The present invention does not define the in-domain route inquiry. Inthe following, the present invention will be described in further detailwith reference to the accompanying figures and three embodiments.

The First Embodiment

The method of the hierarchical route inquiry in accordance with presentembodiment includes the following steps:

Step 1: the RC of the NE in the local route domain detects and receivesa Route Request, then proceeding to the next step;

The Route Request includes the information of the starting node and theending node.

Step 2: according to the Route Request, the RC calls the routingalgorithm, such as CSPF, to calculate the route based on the RDB of thecurrent node, and if the complete route is obtained, the calculatedroute is returned to the requester (such as CC), ending; otherwise, theRoute Request is forwarded to the RC of the parent domain, andproceeding to the next step;

Step 3: according to the Route Request, the RC of the parent domaincalls the routing algorithm to calculate the route based on the RDB ofthe current node, and if the complete route is obtained, the route isreturned to the requester, ending; otherwise, the Route Request isforwarded to the RC of one of its other child domains other than the RCwhich launches the request, and proceeding to the next step;

Generally, the RC of the parent domain forwards the Request to the RC ofthe representative NE in other child domains, and the representative NEis always called as SPEAKER in standards and represents the child domainto interact with the upper-layer route domain, and the RC of therepresentative NE has the information of the upper-layer route domain.All representative NEs constitute the upper-layer route domain.

Step 4: according to the received Route Request, the RC of the otherchild domain calls the routing algorithm to calculate the route based onthe RDB of the current node, and returns the Route Response to the RC ofthe parent domain;

Step 5: the RC of the parent domain determines whether the RouteResponse returned from the RC of the child domains is the completeroute, if yes, the complete route is returned to the requester whichlaunches the Route Request, ending; otherwise, proceeding to the nextstep;

Step 6: the RC of the parent domain determines whether there is still aRC of other child domains that has not been inquired, if there is, theRoute Request is forwarded to the RC of one of the other child domains,and turning to step 4; if the RCs of all child domains has performed theroute inquiry and there is no proper result, a failure message isreturned to the requester which launches the Request, ending.

The embodiment 1 will be described-below in detail by combining FIG. 1,FIG. 2, FIG. 3, FIG. 4 and FIG. 7, taking the route shown with the dotline in FIG. 2 needs to be queried as an example. The ASON NE A in theroute domain only has the information of the route domain 1, the ASON NEB is the representative NE for the route domain 1, while the ASON NE Gfor the route domain 2, the ASON NE I for the route domain 3, the ASONNE M for the route domain 4.

The specific steps are as follows:

Step 1: The RC of the each ASON NE in the route domains 1, 2, 3 and 4checks the Route Request. The RC of the NE A in the route domain 1receives the Route Request, and the starting node is A and the endingnode is K, and proceeding to the next step;

Step 2, the RC of the NE A calls the routing algorithm according to theRoute Request to calculate the route based on the RDB of the currentnode, and if the complete route can not be obtained since theinformation in the RDB of the NE A is not enough, the RC will forwardthe Route Request to the RC of the parent domain, that is, the RC of theNE B, and proceeding to the next step;

Step 3: the RC of the NE B calls the routing algorithm according to theRoute Request to calculate the route based on the RDB of the currentnode, and if the complete route is obtained, the Route Response isreturned to the RC of the NE A, ending. Otherwise, the Route Request isforwarded to the RC of the NE G in the route domain 2;

Step 4: the RC of the NE G calls the routing algorithm according to thereceived Route Request to calculate the route based on the RDB of thecurrent node, and if the complete route is obtained, the Route Responseis returned to the RC of the NE B, ending. Otherwise, a failure messageis returned to the RC of the NE B;

Step 5, according to the result returned from the RC of the NE G, the RCof B returns the result to the RC of the A if the route is complete,ending; Otherwise, the Request is forwarded to the RC of the NE I in theroute domain 3, and repeating the step 4 and step 5. If all childdomains, including the route domains 2, 3 and 4, have been queried, yetthere is no proper result, then the RC of B returns a failure message tothe RC of A, ending.

If the inquiry is successful, the route should be shown as FIG. 7.

The Second Embodiment

The implementation of the second embodiment can be obtained by partiallymodifying the related steps of the first embodiment, and the secondembodiment includes the following steps:

Step 1: after the RC of the related ASON NE in the local route domaindetects and receives a Route Request, proceeding to the next step;

Step 2: according to the Route Request, the RC calls the routingalgorithm to calculate the route based on the RDB of the current node,and if the complete route is obtained, the route is returned to therequester, ending; otherwise, the Route Request is forwarded to the RCof the parent domain, and proceeding to the next step;

Step 3: according to the Route Request, the RC of the parent domaincalls the routing algorithm to calculate the route based on the RDB ofthe NE, and if the complete route is obtained, the route is returned tothe requester through the RC which launches the Request, ending;otherwise, the Route Request is broadcasted to the RCs of all otherchild domains (typically the RCs of the representative NEs) except theone which launches the request, and proceeding to the next step;

Step 4: according to the received Route Request, the RCs of all otherchild domains call the routing algorithm to calculate the route based onthe RDBs of their current nodes, and return the Route Responses to theRC of the parent domain;

Step 5: if the RC of the parent domain receives the complete routereturned from the RC of one or more child domains, the RC of the parentdomain selects one (if only one RC returns the complete route, there isno need for selection) and returns it to the requester which launchesthe Request, ending; otherwise, a failure message is returned to therequester, ending.

The second embodiment will be described-below in detail by combiningFIG. 1, FIG. 2, FIG. 3, FIG. 5 and FIG. 7 and taking the route shown asthe dot line in FIG. 2 needed to be queried as an example. The secondembodiment is based on the same network as the first embodiment.

The specific steps are as follows:

Step 1: the RC of each NE in the route domains 1, 2, 3 and 4 detects theRoute Request. The RC of the ASON NE A in the route domain 1 receivesthe Route Request, the starting node is A and the ending node is K, andproceeding to the next step;

Step 2, the RC of the NE A calls the routing algorithm according to theRoute Request to calculate the route based on the RDB of the currentnode, and if the complete route can not be obtained since theinformation in the RDB of the NE A is not enough, the RC will forwardthe Route Request to the RC of the parent domain, that is, the RC of theNE B, and proceeding to the next step;

Step 3: the RC of the NE B calls the routing algorithm according to theRoute Request and calculates the route based on the RDB of the currentnode, and if the complete route is obtained, the Route Response isreturned to the RC of the NE A, ending. Otherwise, the Route Request isbroadcasted to the RC of the NE G in the route domain 2, the RC of theNE I in the route domain 3, and the RC of the NE M in the route domain4;

Step 4: if the RC of B receives the complete route from the RC of one ormore child domains, the RC of B selects one of them (if there is onlyone, then there is no need for selection) and returns it to the RC whichlaunches the Request. If there is no complete route returned from routedomains 2, 3, 4, a failure message is returned to the RC of A, ending.

Compared with the example of the first embodiment, in the secondembodiment, the RC of the parent domain applies the parallel mechanismin step 4, that is, the Route Request is simultaneously sent to the RCof each child domain. The route successfully queried in this embodimentis shown as FIG. 7.

The Third Embodiment

The hierarchical route inquiry method of the present embodiment is asegmental inquiry which includes the following steps:

Step 1: the RC of the related ASON NE in the local route domain detectsand receives a Route Request, proceeding to the next step;

Step 2: the RC determines whether it is a cross-domain inquiry request,if no, according to the Request, the RC calls the routing algorithm tocalculate the route based on the RDB of the current node, and thecomplete route is returned to the requester, ending; otherwise, theRoute Request is forwarded to the RC of the parent domain, andproceeding to the next step;

Step 3: according to the Request, the RC of the parent domain calls therouting algorithm to calculate the route based on the RDB of the currentnode, and if the complete route is obtained, then the boundary node ofeach child domain on the route (that is, the information of the startingnode and ending node of the in-domain route inquiry) is determined togenerate the in-domain Route Request of the child domains including theinformation of the starting node and the ending node of thecorresponding child domains and forwards the Request to the RC of thesechild domains, which are always the RCs of the representative NEs, andproceeding to the next step; otherwise, a failure message is returned tothe requester through the RC which launches the request, ending;

The RC of the parent domain generally is configured with the routeinformation among each child domain, that is, each child domain istreated as a network element to calculate.

Step 4: after each child domain receives the Route Request, it calls therouting algorithm to calculate the route based on the RDB of the currentnode, and returns the Route Response to the RC of the parent domain;

Step 5: if the RC of the parent domain receives the Route Response fromthe child domains and the route calculation by each child domain issuccessful, then the RC of the parent domain combines the locallycalculated route between the child domains to generate a complete routefrom the starting node to the ending node, and the route is returned tothe requester through the RC which launches the Request, ending; If theroute calculation by any child domain fails, a failure message isreturned to the requester through the RC which launches the Request,ending.

The third embodiment will be described-below in further detail bycombining FIG. 1, FIG. 2, FIG. 3, FIG. 6, FIG. 7, FIG. 8, FIG. 9, FIG.10 and FIG. 11, taking the route shown as the dot line of FIG. 2 neededto be queried as an example. The third embodiment is based on the samenetwork as the above two embodiments.

The specific steps are as follows:

Step 1: the RC of each ASON NE in the route domains 1, 2, 3 and 4 checksthe Route Request. The RC of the NE A in the route domain 1 receives theRoute Request, and the starting node is A and the ending node is K, andproceeding to the next step;

Step 2, the RC of the NE A determines that the Request is a cross-domainRoute Request and forwards the Route Request to the RC of the parentdomain, that is, the RC of the NE B, and proceeding to the next step;

Step 3: the RC of the NE B calls the routing algorithm according to theRoute Request to calculate the route between the route domains 1,2,4based on the RDB of the current node, and the route result is shown asFIG. 8, which determines the boundaries for the child domains 1, 2 and4, and then the RC of B generates the in-domain Route Request of thechild domains 1, 2, and 4, and broadcast the Request to the NE A in thechild domain 1, the NE G in the child domain 2 and the NE M in the childdomain 4;

Step 4: the RCs of the NE A in the child domain 1, NE G in the childdomain 2 and NE M in the child domain 4 call the routing algorithmaccording to the Route Request to calculate the route based on the RDBsof their current nodes, and the route results are respectively shown asin FIGS. 9, 10 and 11, and the result is returned to the RC of the NE B.

Step 5: the RC of B receives the route results from each child domains1, 2 and 4, as shown in FIGS. 9, 10 and 11. If the route calculation bythe child domains 1, 2 and 4 is successful, then by combining the resultshown in FIG. 8 calculated by step 3, the RC of B generates the completeroute shown as FIG. 7, and returns the result to the RC of A whichlaunches the Request, ending.

Of course, the present invention may have many other embodiments.Therefore, without departing from the spirit and essence of the presentinvention, those skilled in the field can make various correspondingmodifications or variations which will fall into the protection scope ofthe claims of the present invention.

INDUSTRIAL APPLICABILITY

Based on the model of hierarchical route suggested by ITU-T G.8080, thepresent invention performs the route inquiry, especially cross-domainroute inquiry by the interaction between the RC of the parent domain andthe RC of the related NE in each child domain, easy and reliable.

I claim:
 1. A hierarchical route inquiry method in Automatic SwitchedOptical Network (ASON) used in a network comprising multi-layer routedomains, comprising the following steps: (a1) A Route Controller (RC) ofan ASON network element (NE) detects a Route Request launched by arequester, and then forwards the Route Request to a RC of a parentdomain if the Route Request is a cross-domain Route Request; (a2) The RCof the parent domain calculates a route among all its child domains andsends an in-domain Route Request to the RC of each child domain on theroute, the RC of each child domain calculates the route in its domainand returns a Route Response to the RC of the parent domain, afterreceiving the Route Response, the RC of the parent domain returns theroute to the requester through the RC which launches the Route Requestif the complete route can be obtained, otherwise a failure message isreturned.
 2. A method of claim 1, wherein step (a2) further comprisesthe following steps: (a21) The RC of the parent domain calculates theroute among its child domains, determines a boundary node of each childdomain on the route, and then generates and broadcasts the in-domainRoute Request including information of the boundary node correspondingto each domain to the child domains; (a22) After the child domainsreceive the in-domain Route Request, it calculates the route of itsdomain and returns the Route Response to the RC of the parent domain;(a23) After the RC of the parent domain receives the Route Responsesfrom the child domains, it determines whether all of the Route Responsesare successful, if yes, proceeding to the next step; otherwise, afailure message is returned to the requester through the RC whichlaunches the request, ending; (a24) The RC of the parent domain combinesthe cross-domain route and the in-domain route of the child domains togenerate the complete route between a starting node and an ending node,and returns the complete route to the requester through the RC whichlaunches the Request, ending.
 3. A method of claim 1, wherein if theparent domain fails to calculate the cross-domain route in step (a1),the failure message is returned to the requester through the RC whichlaunches the Request, ending.
 4. A hierarchical route inquiry method inAutomatic Switched Optical Network (ASON) used in a network comprisingmulti-layer route domains, comprising the following steps: (b1) After aRoute Controller (RC) of a network element (NE) in ASON detects a RouteRequest sent by a requester, the RC of the NE in ASON calculates a routebased on Route Data Base (RDB) of a current node, and returns a RouteResponse to the requester if a complete route is obtained, ending;otherwise, the Request is forwarded to a RC of the parent domain; (b2)The RC of the parent domain calculates the route based on the RDB of thecurrent node according to the Request, and if the complete route isobtained, the complete route is returned to the requester through the RCwhich launches the Request, ending; otherwise, proceeding to the nextstep; (b3) The RC of the parent domain forwards the Route Request to theRCs of its other child domains, and receiving the Route Responsesreturned from the RCs of these child domains, if a complete route can beobtained, the complete route is returned to the requester through the RCwhich launches the Request; otherwise, the failure message is returnedto the requester through the RC which launches the Request, ending.
 5. Amethod of claim 4, wherein step (b3) further comprises the followingsteps: (b31) The RC of the parent domain sends the Route Request to theRC of one child domain except for the one which launches the Request;(b32) After the RC of the child domain receives the Route Request, itcalculates the route based on the RDB of the current node and returnsthe Route Response to the RC of the parent domain; (b33) The RC of theparent domain determines whether the Route Response returned from the RCof the child domain is the complete route, if yes, the route is returnedto the requester through the RC which launches the Request, ending;otherwise proceeding to the next step; (b34) The RC of the parent domaindetermines whether there is a RC of another child domain that has notbeen queried, if there is, the Route Request is forwarded to the RC ofthis child domain, and turning to step (b32); otherwise, the failuremessage is returned to the requester through the RC which launches therequest, ending.
 6. A method of claim 4, wherein step (b3) furthercomprises the following steps: (b31) The RC of the parent domainbroadcasts the Route Request to the RCs of all other child domainsexcept the one which launches the Request; (b32) After the RCs of allother child domains receive the Route Request, they calculate the routebased on the RDBs of the current nodes and return the Route Responses tothe RC of the parent domain; (b33) The RC of the parent domaindetermines whether there is the complete route in the Route Responsesreturned from the RCs of the child domains, if yes, the route isreturned to the requester through the RC which launches the Request,ending; otherwise, the failure message is returned to the requesterthrough the RC which launches the Request, ending.
 7. A method of claim1, wherein when the RC of the parent domain sends the Route Request tothe RC of the child domain, the Route Request is sent to the RC of arepresentative NE which represents the child domain to interact with anupper-layer route domain.
 8. A method of claim 4, wherein when the RC ofthe parent domain sends the Route Request to the RC of the child domain,the Route Request is sent to the RC of a representative NE whichrepresents the child domain to interact with an upper-layer routedomain.